1. Field of the Invention
This invention relates to a method of and apparatus for sensing the temperature of a moving substrate, e.g., a glass ribbon.
2. Brief Description of the Temperature Sensing Technology
U.S. Pat. Nos. 2,007,118; 3,183,718; 3,246,519 and 3,813,515 each teach a device for sensing temperature of a moving substrate, e.g., ribbons and/or wires. A common feature of the devices is one or more thermocouples mounted to a rotating member such that the hot junction of the thermocouple rotates with the member to periodically sense the temperature of the substrate. Although this technique is acceptable, increasing the temperature sensing frequency normally requires increasing the number of thermocouples in the rotating member which increases the cost of these devices.
U.S. Pat. No. 2,618,672 teaches the mounting of a thermocouple within a sleeve with the hot junction of the thermocouple spaced from the sleeve end. The temperature measuring device of U.S. Pat. No. 2,618,672 is acceptable for sensing temperature of a stationary article but is not easily adapted for sensing the temperature of a moving article. This is because contacting the article surface can result in marring the surface.
U.S. Pat. No. 3,309,236 teaches a thermocouple apparatus having a thermocouple mounted in a concave reflective member. The member is mounted between three spaced wheels which wheels ride on the substrate surface to support the hot junction above the surface. The limitation of this type of apparatus is that undulations of a moving substrate, for example, resulting from conveyor wear, can result in varying distances between the hot junction of the thermocouple and the substrate. These variations can result in temperature measurement variations which can lead to erroneous conclusions regarding the substrate temperature.
In view of the above, it would be advantageous to provide a temperature sensing device that does not have the limitations of the above-discussed devices.